A projector is a device for projecting an image onto a target such as a screen. There is a projector which, when projecting an image, measures a distance to a target, and adjusts focusing of an image to be projected. Further, there is a projector which takes a projected image, and adjusts focusing of the image based on the taken image.
Patent reference No. 1 (mentioned later) discloses a technique of using an active sensor, projecting infrared rays onto a target, measuring a distance to the target from the light reception intensity of the reflected light, and adjusting focusing based on the distance.
Patent reference No. 2 (mentioned later) discloses a technique of taking an image of a projected focusing pattern, detecting brightness differences of all the pixels of the taken image data from the adjacent pixels, calculating the sum total of the absolute values of the brightness differences, and moving a focusing lens at a position having the maximum value of the sum total, and thus carrying out automatic focusing adjustment.
Patent reference No. 3 (mentioned later) discloses a technique (mountain climbing autofocus technique) of receiving reflected light of a projected image by a light reception sensor, taking out high frequency components of an electric signal output from the light reception sensor, calculating contrast of an image signal (image data) obtained from integrating and/or the like of the high frequency components and obtaining the position having the maximum contrast as an in-focus point.
When there is an obstruction (a presenter, a desk, or the like) between a projector and a target, or when a wall or the like is close to a side of a target opposite to a side onto which an image is projected, there is a case where an error is included in measurement of the distance to the target carried out using detection of a signal input level of a light reception element, according to the technique disclosed by Patent reference No. 1. Thus, focusing adjustment may not be achieved. Further, according to the techniques disclosed by Patent references Nos. 2 and 3, there is a case where the brightness or the contrast concerning an obstruction has the maximum value, and thus, focusing adjustment may not be achieved using brightness or contrast.